The present invention relates to scrubbers and, in particular, to scrubbers having apparatus to enhance evaporation and reactions occurring within the scrubber.
It is known to employ a scrubber to remove pollutants from an exhaust stream. Known dry scrubbers employ a slurry that is sprayed into a reaction vessel. A typical slurry would be Ca(OH).sub.2. The slurry can react with hydrochloric acid, hydrogen flouride, carbon dioxide, sulfur dioxide and other pollutants to produce a particulate that can be dried into a solid plus water vapor.
These known scrubbers take precautions to ensure the proper evaporation rate within the reaction tower. For this reason the droplet size is carefully controlled so that the evaporation does not occur to early (so the reaction is incomplete) or too late (so wet slurry leaves the reaction vessel).
It is known to use an electric horn to enhance the separation of phases. For example, it has been suggested that a distillation process can be enhanced by establishing sonic vibrations within the distillation column. Analysis suggests that these vibrations increase the rate of interchange between liquids and another fluid phase. However, this technology has not been successfully applied to controlling the evaporation and reaction of droplets in a dry scrubber.
It has also been suggested that sulfuric acid containing waste, can be effectively cracked in a furnace by forming it into a mist that is vibrated ultrasonically by an atomizer that causes vibrations as it atomizes. Such technology, however, is quite different from dry scrubbers and was designed primarily to increase cracking yield, not control evaporation. Furthermore there is no suggestion in this technology how these sonic vibrations ought to be applied in a scrubber.
It has been suggested (U.S. Pat. No. 3,389,971) that a high speed mist can be injected across the path of chimney gas. That system passes a high speed mist into a side outlet to be dumped into a waste tank. This prior art suggests injecting air and water to produce an ultrasonic whistle. The mist so produced, however, is merely water and does not include sorbent. Thus this reference has little relevance to the complicated processes involved in dry scrubbers.